A Family Affair

While many parents of children with autism want to know more about the possible role of environmental factors in the development of the condition, scientific studies show that perhaps as much as 90 percent of the risk comes from genes. Autism is highly heritable, an observation underscored by the fact that, among the younger siblings of kids with autism, roughly 10 percent will also develop the disorder. But what about the other 90 percent? "They're the ones that interest us," says Karen Dobkins, professor of psychology at the University of California, San Diego. Their quirky behavior is not enough to qualify for a diagnosis of autism, but "they still show atypical patterns of social interaction and communication," she says. What's going on in their brains? And can it yield any clues that might help lead to earlier diagnosis for those with the full-blown autism?

This week, Dobkins and her colleague Leslie Carver unveiled two joint studies at the International Meeting for Autism Research that, in different ways, help to chip away at those questions. In one of the studies, the pair looked at social behaviors; in the other, at sensory perceptions. But both are highly revealing.

The first of the studies examined a behavior known as "social referencing"—or the tendency to look to others to help read meaning into an unfamiliar event. Dobkins explains it this way. "Say, you've never flown in an airplane before and it starts bouncing around," she says. You're not sure if this means you've hit a rough patch or the plane is about to nosedive. "So you look around at your fellow passengers," she says. "If they're screaming, you think, 'This is bad. I have to start screaming, too'."  This behavior is very common. Children usually begin doing it around 12 months of age, checking for mom's smile of approval before investigating a new caterpillar in the park, for example.

But in a study of 20 "high-risk" toddlers (18-month-old children with an autistic older sibling), Carver and Dobkins showed that the social-referencing behavior of these children was very different from that of a control group of 16 children the same age with no autism in the family. They put each child into a room with a parent, a researcher (who was a stranger) and a series of novel mechanical toys—a spider with eyes that light up and flash, a raccoon that pushes a ball around the room with its nose, and a dinosaur that walks in circles and beeps. Both groups stared intently at the toys for a good 30 seconds or so before looking up at the parent for cues as to how to interpret these puzzling creatures. But the children with no autism in the family looked at the stranger 2.5 times more often than the high-risk children did. Why? Carver speculates: "The high-risk toddlers might be comfortable with their moms, but less comfortable with a complete stranger."

Even more intriguing was their response to the cues from the adults. When the stranger registered delight or disgust or showed no particular emotion at all, the children in the control group responded accordingly, reacting more positively to a toy "tagged" with a positive emotion, more negatively to one that drew negative responses from the adult stranger. But the high-risk toddlers simply ignored the cues. "There was no match of emotions," says Carver. "Again, we think that one of the things in autism is being able to read emotions, know what they mean and apply them to social situations."

That's not all the study revealed. The toddlers all wore caps with tiny electrodes embedded in them to record brain waves—and those, too, showed differences. The control-group children had three different types of brain-wave responses, depending on the emotions the researcher displayed—positive, negative or neutral. But the high-risk children showed identical patterns of brain activity in response to all three. This is particularly interesting, says Carver, because these are not children that have been identified as quirky or problematic or anything but normal. Yet there are clearly differences there. "We often note that adult family members of kids with autism don't like big crowds or avoid parties or prefer to work with data than people," she says. None of these behaviors constitutes a diagnosis. "But it shows social inhibition"—and that may run in families.